Title: High-resolution ultrasonic imaging of dose distribution in clinical gel dosimeters Short title: Ultrasonic imaging of dose distribution Project summary Luna Innovations in partnership with Carilion Health System proposes to develop and test a high-resolution ultrasonic technique for non-invasive 3D characterization of absorbed dose distributions in clinical gel dosimeters. Radiation-induced degradation of gel properties is an efficient way to capture spatial dose distribution that can be revealed via post processing. The ability to store 3D dose information is a clear advantage over conventional dosimetry techniques, such as water calorimetry, ion chambers, and film-based methods. However, currently deployed post-processing methods using magnetic resonance imaging and optical tomography are expensive and require lengthy off-site processing. The proposed method is based on accurate ultrasonic signal phase measurement technology that can detect changes in sound speed caused by variations in material properties with better than 20 parts per billion precision. It will offer low-cost, near-real-time, on-site interpretation of dose information stored in gel with very high spatial resolution and dose accuracy. In Phase I we will assemble a proof-of concept ultrasonic scanning system, prepare gel samples with dose distribution memory, and collect ultrasonic through-transmission signals according to the fan beam tomographic geometry on several custom gel samples subjected to ionizing radiation in clinical environment. We will reconstruct spatial distributions of absorbed dose and compare them to the actual dose measured with a conventional scanning ion chamber technique. We will also study the spatial resolution and dose sensitivity of the method as well as its ability to correctly handle refraction and boundary transition artifacts. In Phase II we will develop a circular transducer array-based portable prototype for clinical testing and optimize formulation of a radiation sensitive gel for ultrasonic assessment. An array-based prototype will allow for rapid imaging of dose distribution in standardized gel samples with minimum of equipment - potentially a single box with USB link to a laptop. The new technology will address the need for quick and accurate on-site calibration of modern radiation treatment equipment, resulting in increased throughput and efficiency of future cancer treatment procedures. Title: High-resolution ultrasonic imaging of dose distribution in clinical gel dosimeters Short title: Ultrasonic imaging of dose distribution Relevance: The proposed ultrasonic characterization of absorbed dose in polymer gel phantoms will enable rapid and accurate on-site calibration of modern radiation treatment equipment and help increase throughput and efficacy of future cancer treatment procedures. The ultimate goal is to provide accurate beam profile measurement in real time to interactively adjust multileaf collimator settings. [unreadable] [unreadable] [unreadable] [unreadable]